272 



NA TURE 



[January 19, 1899 



FOSSIL VERTEBRATES IN THE AMERICAN 

 MUSEUM OF NATURAL HISTORY. 



IN May 1891, the American Museum of Natural 

 History began to form its historical rnllcitinn of the 

 Fossil Vertebrates of North 

 America. The new department 

 of \'ertebrate Pateontology was 

 established for this purpose, and 

 the Curator organised a series 

 of expeditions to different form- 

 ations in the Rocky Mountain 

 region, beginning with the older 

 tertiaries, and mainly under the 

 direction in the field of Dr. J. L. 

 Wortman, the well-known col- 

 lector and investigator. Between 

 i8gi and 1897 twenty distinct 

 expeditions have been sent out, 

 in several instances the same 

 regions being revisited two or 

 three times, with the object of 

 securing complete material of 

 certain types. In i894andi8g5, 

 and upon a larger scale in 1897, 

 the explorations were extended 

 into the Mesozoic rocks for 

 fossil reptiles. But the main 

 strength of the work hitherto 

 has been among the fossil 

 mammals, and the Eocene and 

 Oligocene collections are now 

 especially complete, embracing 

 the remains of 3000 individuals 

 determined stratigraphically 

 with accuracy, and establishing 

 several new sub-horizons of 

 great importance. In 1895 the 

 famous series of mammalian 

 fossils brought together by the 

 late Prof. Cope was added to 

 these collections, embracing 

 types of 555 species and upwards 

 of 6000 individual specimens. 



There are many sides of this 

 work of interest to the verte- 

 brate paUeontologist, but we 

 may describe here only the 

 effort which has been made to 

 secure for the Museum complete 

 skeletons of the most typical 

 forms in different geological 

 periods. To every one familiar 

 with the rarity of the older Ter- 

 tiary types, the difficulty of this 

 undertaking will be at once ap- 

 parent. It is very seldom indeed 

 that a complete skeleton like 

 that of Pliciiacodus is found 

 together in the older rocks. In 

 ninety-nine cases out of a hun- 

 dred, the skeletons are largely 

 or wholly dissociated. .Another 

 difificulty is, that in the rare 

 cases of association the skeletons 

 are apt to be severely crushed 

 beyond the possibility of recon- 

 struction. In such cases only a 

 drawing can be made. Des])itt 

 all this the Museum has suc- 

 ceeded by persistent attacks 



upon one horizon after another, and by superior methods 

 of field work, in securing a very representative series of 

 complete skeletons partly belonging to single individuals, 



NO. 1525, VOL. 59] 



in some types to three or four different individuals, and 

 in other types, as in the skeleton of Telcpcerus, to a very 

 large number of individuals. With the arrival in the 

 Museum of this material in the crude condition from the 



tu'ld li;n r arisen tlic inerhnnirril firoblcnis of mounting 



these skeletons in vaiious ways. This has received pro- 

 longed study, and after numerous experiments and some 

 failures has now reached a high degree of perfection. 



